Skip-stitch mechanisms for sewing machines



Nov. 1, 1955 E. POFFENBERGER 2,722,186

SKIP-STITCH MECHANISMS FOR SEWING MACHINES Filed Sept. 22, 1952 3 Sheets-Sheet 1 INVENTOR. 3 Everett Poffenbez/yer WITNESS BY ATTORNEY Nov. 1, 1955 E. POFFENBERGER 2,722,186

SKIP-STITCH MECHANISMS FOR sswmc MACHINES Filed Sept. 22, 1952 3 Sheets-Sheet 2 INVENTOR.

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SKIP-STITCH MECHANISMS FOR SEWING MACHINES Filed Sept. 22, 1952 3 Sheets-Sheet 3 ATTORNEY United States Patent SKIP-STITCH MECHANISMS FOR SEWING MACHINES Application September 22, 1952, Serial No. 310,777 Claims. (Cl. 112-200) The present invention relates to sewing machines and has for a primary object to provide, in a sewing machine, mechanism whereby the operator may selectively interrupt the normal stitch-forming operation thereof while the machine continues to run and thus stop making stitches for any desired interval to form a discontinuous seam.

In many sewing operations it is necessary to form discontinuous seams, for example, as in joining the leg portion to the bib portion by the use of a band in the manufacture of overalls. Heretofore, it has been necessary in order to obtain such a seam, to stop the machine and manually shift that portion of the work which is not to be sewed past the stitching mechanism, and then to resume sewing. As will be obvious, this is a time consuming operation that, when repeated several times, adds materially to the cost of the finished garment. In accordance with the present invention, this operation has been substantially eliminated since the machine can now continue to advance the work through that portion which is not to be stitched, and with the mechanism herein disclosed properly actuated the machine will fail to make stitches over the desired length.

More specifically, it is an object of the present invention to provide mechanism in a chain-stitch sewing machine whereby the looper may be selectively moved into such position while the machine continues to operate that it will fail to seize the loop cast out by the needle-thread and thus fail to form stitches.

Having in mind these and other objects that will be evident from an understanding of this disclosure, a H

presently preferred embodiment of the invention is hereinafter set forth in such detail as to enable those skilled in the art to readily understand the function, operation, construction and advantages of it, when read in conjunction with the accompanying drawings wherein:

Fig. l is a fragmentary view partly in elevation and partly in section of the head end of a sewing machine in which the present invention has been incorporated.

Fig. 2 is a fragmentary head end elevation view of a portion of the sewing machine of Fig. 1.

Figs. 3 and 4 are fragmentary section views taken substantially on the line 3-3 of Fig. 1 with the parts illustrated in different operative positions.

Fig. 5 is a fragmentary section view taken on the line 5-5 of Fig. 3.

That portion of the sewing machine illustrated in the drawings comprises a head 1 carried by a bracket-arm 2 which, in the usual manner, surmounts a standard (not shown) that rises from the bed 3. Mounted in the head 1 in the usual fashion is a longitudinally reciprocating needle-bar 4 which carries two pairs of needles 5 at its lower end. A conventional resser-foot 6 is carried by a presser-bar 7 which is also mounted for longitudinal movement in the head 1 in the usual manner.

Adjacent the head end of the machine, the bed 3 is proing gear teeth which mesh vided with a slide-plate 8 which can be removed to per- 1 mit ready access to the underlying mechanism, and immediately under the resser-foot 6 there is provided a throatplate 9. Acting through suitable slots in the throat-plate 9 is a feed-dog 10 which cooperates with the presser-foot 6 to effect feeding-of the work past the stitching mecha- I nism, which feed-dog 10 is carried at the end of a feedbar 11. The feed-dog is actuated through the normal four motion cycle by mechanism which is not herein described and is only illustrated in the drawings insofar as it incidentally appears since it forms no part of the present invention. For a complete disclosure of the feeding mechanism, reference may be had, for example, to the U. S. patent of Zeier, No. 2,292,258, August 4, 1942.

Journaled in suitable bearings provided in the depending walls of the frame portion of the bed 3 of the machine is a main shaft 12 having a crank 13 fixed to the end thereof, which crank 13 is provided with a stud-like crank pin 14. Journaled upon the end of the crank pin 14 is the strap portion of a link 15 which at its other end is pivotally connected to one end of a rock-arm 16 having a strap portion at its opposite end which is fixed to a sleeve 17. The sleeve 17 surrounds a looper fulcrum-rod or shaft 18 fixed eccentrically at its opposite ends in enlarged shaft end-sections 19 and 20. Formed integral with the sleeve 17 is a counterbalanced looper-carrier 21 to which a looper-carrying bar 22 is secured as by a screw 23. Loopers 24, adapted to cooperate with the respective needles 5 in the formation of two-thread chain stitches, are secured to the looper-carrying bar 22.

The shaft end-sections 19 and are rotatably mounted in suitable depending walls of the frame of the machine and the unitary assembly comprising the sections 19 and 2t and shaft 18 is made to rotate by means of a gear 25 which is fixed to the reduced end 26 of the end-section 19 as by a set screw 27 passing through the hub 28 of the gear. The end-section 19 is restrained against axial movement by a plate 29 formed as a segment of an annulus that is adapted to be fixed to the frame of the machine as by screws 30 and to be partially received within a peripheral groove 31 formed in the end-section 19. Formed longitudinally of the end-section 19 is a groove 32 which is intersected by a peripheral groove 33 normal thereto. A

plunger 34 is fitted into a horizontal bore 35 in the frame of the machine and is adapted to have the end thereof extend into the groove 33 and to abut against that edge of the slot 32 opposite the groove 33. As seen in Fig. 5, for instance, the plunger is urged inwardly by a coil spring 36 surrounding the same, which acts between a shoulder 37 on the plunger and a sleeve-like bolt 38 also loosely surrounding the plunger and screwed into the bore 35. A thumb-nut 39 is provided which may be readily grasped by the operator which will facilitate withdrawing the plunger.

To effect rotation of the gear 25 there is provided a rack 40 which is slidably mounted in a suitable bore formed in the frame of the machine and including dependwith the teeth of gear 25. The rack 40 is urged outwardly with respect to the machine by a spring 41 which surrounds the shaft thereof and acts between the headed end of the shaft and the machine frame. There is also provided a radial arm 42 which is secured to the face of the gear 25, as by screws 43, which arm is adapted to be secured by a chain or similar connector to a foot treadle or knee treadle, whereby looper throw-out will be facilitated.

' Operation During normal operation of the sewing machine, the rack 40 is urged outwardly by the spring 41 to its stop position which is that position in which the tip of the plunger 34 is in contact with the side of the groove 32 immediately opposite the groove 33, as illustrated in Fig. 3. It will be noted that the elements are so designed that when they are in this position the loopers will be actuated during operation of the machine through the normal paths and stitch formation will occur. When it is desired to'discontinue stitch formation, the rack 40 is pushed inwardly against the action of the spring 41, or the radial arm 42 is rotated counterclockwise as by actuating a foot treadle, to rotate the gear 25 and consequently the endsection 19 in a clockwise direction as seen in Fig. 4 during which rotation the tip of the plunger 34 moves away from .the stop-edge of the groove 32 and rides in the peripheral groove .33 into that position illustrated in Fig. 4. Since the looper-fulcrum shaft 18 is carried eccentrically by the end-sections 19 and 20, rotation of the end sections moves the shaft 18 bodily to a lowered position, and thus, since the shaft 18 .is the fulcrum for the loopers 24, the path of the loopers is lowered away from .the needles. For comparison, one position of the loopers during .a normal sewing cycle is illustrated in Fig. .2 in full lines, while the same position in the cycle but with the elements shifted to the inoperative position is illustrated in dotted lines. In this latter position, the correct timing of the movement of the looper with respect to the movement of the needle necessary for loop-seizure has been destroyed, and also, the path of the looper has been altered to such an extent that the loopers do not pass close enough to the needle to permit loop seizure.

As long as the elements are held in the inoperative position, as by holding the radial arm 42 down or holding the rack 40 in, the machine will not form stitches but will continue to operate to feed the work past the stitching mechanism. When it is desired to resume stitching, the operator need only to release the rack 40 or the radial arm 42, whichever had been used to hold the elements in inoperative position, and the spring 41, acting to retract the rack 40, will restore the elements to operative position, which is that position illustrated in Fig. 3.

It should also be noted the loopers can be moved to a third position in which they are readily accessible for threading. This position is attained by retracting the locking plunger 34 and then pulling the rack 40 outwardly to rotate the gear 25 in a counterclockwise direction as seen in Fig. 3, whereupon the fulcrum shaft 18 is shifted forwardly and downwardly with respect to the work supporting surface of the bed 3. The machine may then be slowly turned over by hand until the loopers are in their most readily accessible position.

Although the invention is herein illustrated as embodied in a four-needle two-thread chain-stitch sewing machine, it is to be understood, as will be obvious to those skilled in the art, that the invention is not limited to the same but could be used with a single needle two-thread machine and even a single thread chain-stitch machine. The illustrated embodiment has been selected only because this machine has been designed to perform an operation in which a discontinuous seam is especially useful.

Numerous alterations of the structure herein disclosed will suggest themselves to those skilled in the art. However, it is to be understood that the present disclosure relates to a preferred embodiment of the invention which is 'for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.

Having thus set forth the nature of this invention, what I claim herein is:

1. In a sewing machine having a reciprocating needle and a threaded oscillating looper adapted to normally cooperate therewith in the formation of stitches, a shaft end-section rotatable in both directions from a normal stop position, a fulcrum-shaft carried eccentrically by said end-section with the axis thereof substantially parallel to the axis of rotation of said end-section, said looper b ing journaled for oscillation on said fulcrum-shaft, means for imparting oscillation to said looper, and means for rotating said end-section in one direction during operation of the sewing machine to suspend stitch formation and in the other direction to render the looper readily accessible for threading.

2. In a sewing machine, a rotatable shaft end-section, a shiftable fulcrum-shaft carried eccentrically by said endsection with the axis thereof substantially parallel to the axis of rotation of said end-section, a looper journaled on said fulcrum-shaft for oscillation, means for imparting oscillation to said looper, stop means operatively associated with said end-section for limiting rotation thereof to a normal sewing position, resilient means operatively connected to said end-section for rotatably urging the same into a stop-position defined by said stop means, and manual means operatively associated with said end-section for rotating the same away from stop-position during oscillation of said loopers to shift said fulcrum-shaft about the axis of said end-section and thereby modify the path of oscillation of said looper to interrupt normal sewing. 3. In a sewing machine, a rotatable shaft end-section, a shiftable fulcrum-shaft carried eccentrically by said end section with the axis thereof substantially parallel to the axis of rotation of said end-section, a looper journaled on said fulcrum-shaft for oscillation, means for imparting oscillation to said looper, stop means operatively associated with said end-section for limiting rotation thereof to a normal sewing position, a gear secured to said endsection, a slidable rack cooperating with said gear to rotate said end-section away from stop-position during oscillation of said looper upon actuation of said rack to shift said fulcrum-shaft about the axis of said end-section and thereby modify the path of travel of said looper to interrupt normal sewing, and resilient means operatively connected to said rack for urging said end-section into stop-position.

4. In a sewing machine, a rotatable shaft end-section, a shiftable fulcrum-shaft carried eccentrically by said end section with the axis thereof substantially parallel to the axis of rotation of said end-section, a looper journaled on said fulcrum-shaft for oscillation, means for imparting oscillation to said looper, stop means operatively connected with said end-section for limiting rotation thereof to a normal sewing position, resilient means operatively connected to said end-section for rotatably urging the same into a stop-position defined by said stop means, and manual means operatively associated with said end-section for rotating the same away from stop-position during oscillation of said loopers to shift said fulcrum-shaft about the axis of said end-section and thereby modify the path of oscillation of said looper to interrupt normal sewing, said stop means comprising a peripheral groove in said end-section, said groove having an end-wall, and a plunger riding in said groove and cooperating with said end wall. 5. In a sewing machine, a rotatable shaft end-section, a shiftable fulcrum-shaft carried eccentrically by said endsection with the axis thereof substantially parallel to the axis of rotation of said end-section, a looper journaled on said fulcrum-shaft for oscillation, means for imparting oscillation to said looper, stop means operatively connected with said end-section for limiting rotation thereof to a normal sewing position, resilient means operatively connected to said end-section for rotatably urging the same into a stop-position defined by said stop means, and manual means operatively associated with said end-section for rotating the same away from stop-position during os cillation of said loopers to shift said fulcrum-shaft about the axis of said end-section and thereby modify the path of oscillation of said looper to interrupt normal sewing, said stop means comprising a peripheral groove in said endsection, said groove having an end-wall, a plunger riding in said groove and cooperating with said end-wall to define a stop-position, resilient means for biasing said plunger into said groove, and manual means for retracting said plunger against the action of said resilient means for releasing the end-section for rotation beyond the stop-position.

References Cited in the file of this patent UNITED STATES PATENTS 1,915,923 Clayton June 27, 1933 

